1. Field of the Invention
The present invention generally relates to transmitting apparatus and, more particularly, is directed to a transmitter which is driven by battery power.
2. Description of the Prior Art
Recently, various kinds of communication apparatus mounted on a mobile station such as automobiles and so on or portable communication apparatus have been developed so far. Since this kind of communication apparatus for a mobile station or portable communication apparatus is not supplied with an AC voltage, such mobile or portable communication apparatus is generally supplied with and driven by a drive voltage from a housed secondary battery. The secondary battery will hereinafter simply referred to as a battery.
In such communication apparatus driven by battery power, there is a risk that the transmission becomes impossible when an output voltage of battery is lowered during transmission. That is, if the amount of voltage consumed by the communication exceeds the charged amount of the battery, then the output voltage is lowered than the voltage necessary for transmission. As a consequence, the communication apparatus becomes unable to operate unless the battery is exchanged or charged. If the output voltage of the battery is lowered during transmission, then the transmission is ended before it reaches to the end an only one portion of transmission data is transmitted to the receiving side so that reception error occurs in the receiving side. In that event, if the communication apparatus is utilized as a standard telephone to transmit an audio signal, then the user (caller) can immediately notice that the battery is dead because the user directly utilizes this communication apparatus. Therefore, the user can be substantially prevented from being troubled even when the battery is dead. On the other hand, if such reception error occurs during the communication of various data, then the receiving side cannot be controlled at all by the transmission data. Also, there is little possibility that the user can notice that the battery is dead, which considerably troubles the user.